Field of the Invention
The present invention relates to an automatic transmission for a vehicle. More particularly, the present invention relates to a planetary gear train of an automatic transmission for a vehicle that improves power delivery performance and fuel economy by achieving eight forward speed stages with a minimum number of constituent elements being used, and improves silent driving of the vehicle by using operation point positioned at a low engine speed.
Description of Related Art
Recent increases in oil prices are triggering stiff competition among auto-makers in enhancing fuel consumption of a vehicle.
Therefore, research is being conducted on engines in terms of reducing weight and improving fuel efficiency by down-sizing, and research is also being conducted to ensure both drivability and competitiveness for maximizing fuel efficiency by implementing an automatic transmission with multiple speed stages.
However, in the case of an automatic transmission, as the number of speed stages increase, the number of internal components increases, which may deteriorate installability, production cost, weight and/or power flow efficiency.
Accordingly, development of a planetary gear train which achieves maximum efficiency with a small number of components is important in order to increase a fuel economy enhancement effect through the multiple-speeds.
In this aspect, in recent years, 8-speed automatic transmissions tend to be implemented and the research and development of a planetary gear train capable of implementing more speed stages has also been actively conducted.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.